The present invention relates generally to methods and apparatus for storing hydrogen isotopes as hydrides and relates more particularly to methods and apparatus for storing tritium safely and for stagewise separation of hydrogen isotopes from each other. The invention is a result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
It has been known to use copper metal to plate stainless steel in order to prevent the eutectic formation of uranium and iron, which formation had been a metallurgical problem at elevated temperatures. This plating was disclosed, for example, in Los Alamos National Laboratory Report LA-5526-MS, "Shipping Cask for Fast Reactor Fuel Elements," March, 1974 on page 7 on work performed by John W. McMullen et al., as reported by Horace E. Noyes.
A desired objective has been a design suitable for storing all hydrogen isotopes including protium, deuterium, and tritium as uranium hydrides and subsequent recovery of the hydrogenous gases by dehydriding. Specifically, the storage of deuterium and tritium (DT) gas as U(D,T).sub.3 followed by the subsequent recovery of DT gas was desired. For magnetic fusion energy reactor development requirements, pumping, storing, and purifying of deuterium and tritium gases are needed, as well as the capability of scavenging low levels of tritium from inert gas streams. Another desired capability was isotopic separation of hydrogen isotopes.
Additionally, as a hydrogen economy becomes a reality with depletion of oil and gas natural stocks in the world, there will be a large need for beds for storing hydrogen in a safe manner. Beds which utilize uranium (either depleted or natural) are thought to be suitable for such a use as well.
Earlier in the 1970's, because of tritium gas storage needs for research purposes, Lawrence Livermore National Laboratory developed a certified uranium trap (referred to herein as Livermore design), which is described in detail in M. F. Singleton et al., "Traps for Scavenging Hydrogen Isotopes," Proceedings of the Third Topical Meeting on the Technology of Controlled Nuclear Fusion, Volume 2, May 9-11, 1978, Sante Fe, NM, pages 706-713 at page 710. The design described there uses a piece of stainless steel which is bored. In each of seven individual boreholes, three layers of uranium exist, spaced apart by porous frits. An inlet gas line opens into a chamber under the frit at the bottom of the trap; and gas flows upwardly through the seven columns of uranium, into another chamber above the top frit, and into the outlet line. The trap is surrounded by two alternating heating and cooling coils. The size of this particular trap is similar to a so-called "original uranium trap" which also had been developed at Livermore and which contained approximately 1800 grams of uranium in a volume of 1.5 liters.
This uranium trap, however, was found to possess certain disadvantages. First of all, its size was quite small (with a theoretical maximum storage capacity of 68.6 g of tritium). Additionally, the cooling coil which housed the gas used for cooling in the secondary cooling system possessed the following serious disadvantage: if the hydride bed were to burst, it could contaminate the gas in the cooling coil (the argon used, in this case) which could escape the system and could cause a safety hazard. Also, a larger safety margin for temperatures was desired than was possible in that design because of the iron and uranium eutectic formation. Furthermore, cryogenic temperatures needed for cooling the bed required cryogenic gas handling and bed operational dependency on cryogenic gas supplies.
Therefore, an improved design for a hydride bed was sought.